1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
|
/*
Copyright (c) 2010 James Ahlborn
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
package com.healthmarketscience.jackcess.impl;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.charset.Charset;
/**
* Default implementation of CodecProvider which does not have any actual
* encoding/decoding support. See {@link CodecProvider} for details on a more
* useful implementation.
*
* @author James Ahlborn
*/
public class DefaultCodecProvider implements CodecProvider
{
/** common instance of DefaultCodecProvider */
public static final CodecProvider INSTANCE =
new DefaultCodecProvider();
/** common instance of {@link DummyHandler} */
public static final CodecHandler DUMMY_HANDLER =
new DummyHandler();
/** common instance of {@link UnsupportedHandler} */
public static final CodecHandler UNSUPPORTED_HANDLER =
new UnsupportedHandler();
/**
* {@inheritDoc}
* <p>
* This implementation returns DUMMY_HANDLER for databases with no encoding
* and UNSUPPORTED_HANDLER for databases with any encoding.
*/
public CodecHandler createHandler(PageChannel channel, Charset charset)
throws IOException
{
JetFormat format = channel.getFormat();
switch(format.CODEC_TYPE) {
case NONE:
// no encoding, all good
return DUMMY_HANDLER;
case JET:
case OFFICE:
// check for an encode key. if 0, not encoded
ByteBuffer bb = channel.createPageBuffer();
channel.readPage(bb, 0);
int codecKey = bb.getInt(format.OFFSET_ENCODING_KEY);
return((codecKey == 0) ? DUMMY_HANDLER : UNSUPPORTED_HANDLER);
case MSISAM:
// always encoded, we don't handle it
return UNSUPPORTED_HANDLER;
default:
throw new RuntimeException("Unknown codec type " + format.CODEC_TYPE);
}
}
/**
* CodecHandler implementation which does nothing, useful for databases with
* no extra encoding.
*/
public static class DummyHandler implements CodecHandler
{
public boolean canEncodePartialPage() {
return true;
}
public boolean canDecodeInline() {
return true;
}
public void decodePage(ByteBuffer inPage, ByteBuffer outPage,
int pageNumber)
throws IOException
{
// does nothing
}
public ByteBuffer encodePage(ByteBuffer page, int pageNumber,
int pageOffset)
throws IOException
{
// does nothing
return page;
}
}
/**
* CodecHandler implementation which always throws
* UnsupportedCodecException, useful for databases with unsupported
* encodings.
*/
public static class UnsupportedHandler implements CodecHandler
{
public boolean canEncodePartialPage() {
return true;
}
public boolean canDecodeInline() {
return true;
}
public void decodePage(ByteBuffer inPage, ByteBuffer outPage,
int pageNumber)
throws IOException
{
throw new UnsupportedCodecException("Decoding not supported. Please choose a CodecProvider which supports reading the current database encoding.");
}
public ByteBuffer encodePage(ByteBuffer page, int pageNumber,
int pageOffset)
throws IOException
{
throw new UnsupportedCodecException("Encoding not supported. Please choose a CodecProvider which supports writing the current database encoding.");
}
}
}
|
